Modular memories are commonly used in computers and other electronic systems that may require after-market storage-capacity expansion. For example, multiple memory-module sockets may be coupled to a memory controller via a shared memory channel, with each socket being coupled to the memory channel via a stub path. Memory modules are initially installed in fewer than all the sockets so that one or more additional modules may be inserted later to increase (expand) the system storage capacity. Unfortunately, the stub path coupling each socket to the shared memory channel may present a substantial source of undesired noise (especially signal reflections), and thus limit signaling rates and therefore peak memory bandwidth.
Although separate, replicated memory channels could be coupled point-to-point between the controller and respective memory-module sockets, that approach multiplies the number of controller interface pins and external signal lines by the number of memory-module sockets, driving up cost and limiting the number of expansion sockets that can be supported.